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1‐Aminocyclopropane‐1‐carboxylic oxidase (ACCO) is a non‐heme iron(II)‐containing enzyme involved in the biosynthesis of the phytohormone ethylene, which regulates fruit ripening and flowering in plants. The active conformation of ACCO, and in particular that of the C‐terminal part, remains unclear and open and closed conformations have been proposed. In this work, a combined experimental and computational study to understand the conformation and dynamics of the C‐terminal part is reported. Site‐directed spin‐labeling coupled to electron paramagnetic resonance (SDSL‐EPR) spectroscopy was used. Mutagenesis experiments were performed to generate active enzymes bearing two paramagnetic labels (nitroxide radicals) anchored on cysteine residues, one in the main core and one in the C‐terminal part. Inter‐spin distance distributions were measured by pulsed EPR spectroscopy and compared with the results of molecular dynamics simulations. The results reveal the existence of a flexibility of the C‐terminal part. This flexibility generates several conformations of the C‐terminal part of ACCO that correspond neither to the existing crystal structures nor to the modelled structures. This highly dynamic region of ACCO raises questions on its exact function during enzymatic activity. [ABSTRACT FROM AUTHOR]

In the context of developing ecofriendly chemistry, artificial enzymes are now considered as promising tools for synthesis. They are prepared in particular with the aim to catalyze reactions that are rarely, if ever, catalyzed by natural enzymes. We discovered that 1‐aminocyclopropane carboxylic acid oxidase reconstituted with CuII served as an efficient artificial Diels–Alderase. The kinetic parameters of the catalysis of the cycloaddition of cyclopentadiene and 2‐azachalcone were determined (KM=230 μm, kapp=3 h−1), which gave access to reaction conditions that provided quantitative yield and >99 % ee of the (1S,2R,3R,4R) product isomer. This unprecedented performance was rationalized by molecular modeling as only one docking pose of 2‐azachalcone was possible in the active site of the enzyme and this was the one that leads to the (1S,2R,3R,4R) product isomer. [ABSTRACT FROM AUTHOR]

We investigated the effects of host diet on the intestinal persistence and gene expression of L actobacillus plantarum WCFS1 in healthy and health-compromised, 2,4,6-trinitrobenzene sulfonic acid ( TNBS)-treated mice. Mice fed either a low-fat chow diet ( CD) or high fat and sucrose Western diet ( WD) received 109 L. plantarum WCFS1 cells for five consecutive days. L actobacillus plantarum persistence was 10- to 100-fold greater in the intestines of WD-fed compared with CD-fed mice. TNBS, an intestinal irritant that induces the development of inflammatory bowel disease-like symptoms, resulted in up to a 104-fold increase in L . plantarum survival in the digestive tract relative to healthy animals. Expression levels of 12 metabolic and gut-inducible L. plantarum genes were differentially affected by diet and TNBS administration. Pyrosequencing of 16 S rRNA transcripts from the indigenous intestinal microbiota showed that WD resulted in significant reductions in proportions of metabolically active indigenous L actobacillus species and increases in the Desulfovibrionaceae family. Feeding L. plantarum WCFS1 resulted in lower levels of colitis and higher concentrations of colonic IL-10 and IL-12 in WD and not CD-fed mice. Interactions between probiotics, nutritional components and the intestinal bacteria should be considered when examining for probiotic-mediated effects and elucidating mechanisms of probiotic function in the mammalian gut. [ABSTRACT FROM AUTHOR]